Fiber optic transceivers are used in a variety of applications, including storage area networks (SANs), local area networks (LANs), Fibre Channel, Gigabit Ethernet, and synchronous optical networks (SONET) applications. Fiber optic transceivers can be used as the network interface in mainframe computers, workstations, servers, and storage devices. Fiber optic transceivers can also be used in a broad range of network devices, such as bridges, routers, hubs, and local and wide area switches.
Fiber optic transceivers include a fiber optic receiver and a fiber optic transmitter. The fiber optic receiver converts optical serial data to electrical serial data and the fiber optic transmitter converts electrical serial data to optical serial data. A majority of fiber optic transceivers include power control circuits, diagnostic circuits, and other circuits for enhancing the functionality of the fiber optic transceivers.
Fiber optic transmitters include a laser driver and a transmitter optical subassembly (TOSA). Laser drivers provide a bias current and a modulation current to a laser to control the optical output power of the laser. Typically, laser drivers control the bias and modulation currents over temperature and as the laser ages to maintain constant output power of the laser. Laser drivers can be single ended or differential. A single ended laser driver provides the modulation current and the bias current to one side of a laser with the other side of the laser coupled to a common or ground. For a differential laser driver, both sides of the laser are coupled to the laser driver circuit.